to provide a sound, scientific understanding of the primary natural and human factors affecting the quality of these resources (Huntzinger, 1991). In meeting these long-term goals, the program provides water-quality information that will be useful to policy makers and managers at the national, state, and local levels. Sixty study units were identified for water-quality assessment activities. These study units generally correspond to the major river basins throughout the United States (fig. 1). The Central Nebraska Basins study unit was one of the initial 20 started in fiscal year 1991 (Leahy and others, 1990). This study unit includes the Platte River and its tributaries from the confluence of the North and South Platte Rivers at North Platte, Nebraska, downstream to the Missouri River north of Omaha (fig. 2). The U.S. Environmental Protection Agency (USEPA), Region VII, initiated the Platte River Ecosystem Management Initiative (PREMI) in 1990(Elfving, 1992). The Nebraska Department of Environmental Quality (NDEQ) has since joined the USEPA in this effort to address ways in which the Platte River and its ecosystem can be protected and enhanced through improved water-quality management. The focus of the USEPA and the NDEQ in the PREMI is on water quality of the river, its associated riparian areas, and its alluvial aquifer. The goals of the PREMI program are to enhance, maintain, and expand, as necessary, efforts to protect water quality, public health, and the environment in the Platte River Basin of Nebraska through comprehensive and integrated Federal, State, and local environmental program management and implementation. The PREMI study area includes all of the Platte River Basin that is in Nebraska. To help facilitate the current and future waterquality assessment of the USGS's Central Nebraska Basins study unit and the USEPA's Platte River study area, a search of the scientific literature was performed, and more than 1,000 citations of published or unpublished reports, pamphlets, Introduction 1 Sources of Literature Citations 3 records, including dissertations and theses, and is used by almost 14,000 libraries for cataloging purposes (OCLC Online Union Catalog, 1991).
